A nurse is providing teaching to a client who has a new prescription for tetracycline. The nurse should instruct the client to avoid taking which of the following supplements with tetracycline?

A. Calcium carbonate: Calcium binds with tetracycline in the gastrointestinal tract and significantly reduces its absorption, decreasing the antibiotic's effectiveness. Clients should be advised to take tetracycline either 1 hour before or 2 hours after calcium-containing products. B. Vitamin C: Vitamin C does not interfere with the absorption of tetracycline and can be safely taken concurrently. It may even support immune function, but it does not affect the antibiotic’s efficacy. C. Folic acid: Folic acid is a water-soluble vitamin that does not impact tetracycline absorption. There is no interaction that requires separating administration or avoiding concurrent use. D. Fish oil: Fish oil supplements do not contain minerals that bind tetracycline, and there is no known interaction. They can be taken without affecting the antibiotic’s absorption or function.